Production of strips or bands from metal powder



F. HECK April 21,-1959 PRODUCTION OF-ISTRIPS 0 BANDS FROM METAL POWDER 2Sheets-Sheet 1 Filed Sept. 2, 1955 F. HECK April 21, 1959 PRODUCTION OFSTRIPS 0R BANDS' FROMME'IAL POWDER Filed Sept. 2, 1955 2 Sheets-Sheet 2I ////l fill/Ill)! Unite PRODUCTION OF STRIPS OR BANDS FROM METAL POWDERIn the known processes the production of strips and sheets from metalpowder, more particularly copper powder, is effected by first of allconsolidating a layer of powder by means of rolls, so that aself-supporting bandshaped body results. Thereupon, sintering andreconsolidating follows alternately in separate operations by means ofrolls. After finish rolling, an annealing process is applied, ifnecessary.

The finishing of strips presents special difficulties duringreconsolidation by means of rolls. These difliculties are due tothecircumstance, that the strip after the first operation permits ofonly very slight rolling down. During reconsolidation the strips have torun through the rolls without guiding means, as any contact with aguiding element will tend to fold over the edge of the strip and maycause a fracture of the strip. Furthermore it is only possible tooperate with a very slight braking and reeling tension. Any racing ofthe reeling up appliance during winding up may, in the case of heavyrings, result in a destruction of the strip which after the firstoperation is still very brittle. Owing to the great sensitiveness of thecopper strip, when first formed, and the lack of lateral roll tableguides, referred to above, only low rolling speeds can be employed. Theknown methods are thus not very efficient, more particularly, as onlycostly electrolytic copper powder can be used in the process.

The above described disadvantages have led to the consideration, as towhether it might not be possible to make use of cheap copper powderobtained by a wet chemical process. A processing of the copper powderproduced in this way is, however, not readily possible, as the form ofthis powder is globular, whilst the hitherto used electrolytic copperpowder is finely divided. When using a finely divided powder a goodmechanical interlocking of the powder particles is brought about, whichpresents certain difiiculties in the case of a powder of globularformation; for preconsolidated strips formed of globular copper powderhave very slight inherent strength, so that such strips may very easilyfracture. The invention sets out to solve the problem to develop aprocess and an arrangement for enabling copper powder of globularformation, which has been produced by wet chemical means, to be workedup.

According to the invention the metal powder, more particularly copperpowder composed of powder particles of globular formation, is heated toabout red heat and is in this state fed to the roll gap. Theconsolidation and sintering of the powder takes place simultaneouslythrough roll pressure and under the action of heat, the rolls beingheated and giving off their heat to the metal powder which is kept underthe action of a protective gas, for instance H In this arrangement therolls are heated up preferably to a temperature of about 600 C. Incertain circumstances, it is however, possible to heat up the metalpowder only, which during the rolling process continuously gives oifheat to the rolls which by means of their consid- States Patent ICCerable mass store up the heat imparted to them. But these two processesmay also be combined in such a manner that there will be both a directheating up of the rolls and a heating of the metal powder.

An essential feature is thus, that for the sintering process sufiicientheat should be available.

For carrying out this process a particularly suitable rolling mill isone which is provided with obliquely superposed rolls and in which theplane containing the axes of the upper and lower rolls is at an angle tothe vertical of about 25. In such a rolling mill the rolls may bedirectly heated. According to the invention it is therefore proposed tosupport and drive both operative rolls by a number of small rollerswhich are in engagement with the upper and lower convex surfacesrespectively of the operative rolls. Such an arrangement provides thepossibility of strewing on the metal powder laterally from the crown ofthe lower roll, which conveys the powder in a uniform layer to the gapbetween the rolls. In accordance therewith there is provided on theopposite side a delivery duct provided with stripping members extendinginto the roll gap. According to the invention provision must be made forprotecting the metal powder from oxidation. With this object in view,according to the invention the space, through which the said metalpowder runs, is closed to the outside and filled with protective gas.

For the rolls themselves a heat-resisting and non-scaling material mustbe employed. The heating up of the operative rolls may be effected bothwith gas burners and in accordance with the electric resistance weldingprinciple. It is also possible to arrange the two operative rolls aselectrodes.

For the rapid cooling of the rolled strip a cooling space may beprovided on the delivery side.

A rolling mill according to the invention is diagrammaticallyillustrated in the accompanying drawings, in which:

Figure 1 shows the mill as a whole in side elevation;

Figure 2 shows the receiving duct and associated details in sectionalelevation;

Figure 3 is a perspective view of the receiving duct;

Figure 4 shows the feeding duct and cover in sectional elevation; and

Figure 5 is a perspective view of the cover alone.

This rolling mill has two operative rolls 1 and 2, which are supportedand driven by supporting rollers 3. These supporting rollers may have tobe cooled. The two operative rolls are arranged obliquely one above theother. The heating of the operative rolls 1 and 2 is effected by meansof burners 4. Laterally of the crown of the lower roll 2 is the feedinlet or feeding duct 10 for the powder, from which the powder passes onto the convex surface of the operative roll 2 which conveys theuniformly deposited powder in the form of a strip or band to the rollgap. At the end of the powder feed inlet 10 is a covering device 6,including lateral walls 13 shown in Figure 5 the purpose of which is toform a closed space which is filled with protective gas H admitted tothis space, and also to the feeding duct 10, through inlets 14 asindicated, whilst on the under side the metal powder itself acts as aseal. From the orifice of the duct 10 to the roll gap 7 the requisiteheating of the metal powder takes place, which is then consolidated inthe roll gap 7. After leaving the roll gap 7 the consolidated strip orband 12 passes into a channel-shaped cooling space or receiving duct 8which is provided with strippers 9 extending into the roll gap. Theinterior of the cooling space 8 which is in open communication with thespace closed by the cover 6, is also filled with protective gas,admitted through an inlet 15. Provision is also made for a coolingjacket 16 which is swept through, for instance, by cooling water,

3 admitted through an inlet 17 and discharged through an outlet- 18. Thereceiving duct is provided with taperinglateral extensions 19 extendingrearwards past the strippers 9 so as to close the roll gap at the sides.

As already stated; the operative rolls l an'd 2 are in theconstructionalexample illustrated, guided and driven only by rollers 3.This-signifies, that thethick ness' of the roll gap 7 is filled by theamount ofmetal' powder fed'in; the thickness of the roll gap beingdetermined by the position of the guide rollers 3;

For reducing the loss of heat, the operative rolls 1, 2 may be providedwith a housing 11.

I- claim:

1. A rolling millv for producing strips ofmetal from metal powder,particularly copper powder, comprising: two operative rolls arrangedobliquely one above the other, a duct for feeding metal powder to theupper surface ofthe lower roll at a position preceding its highest part,means for heating the rolls to a temperature high enough to sinter themetal powder, a plurality of rollers, of a diameter smaller than that ofthe operativerolls, bearing against the peripheries of the operativerolls so as to support them and urge them towards one another, a duct onthe opposite side of the operative rolls from the feeding duct, adaptedto receive the metal strip formed, and strippers in the receiving duct,bearing against the peripheries of the operative rolls.

2. A rolling mill as claimedv in claim 1, further comprising a cover,enclosing, in conjunction with the feeding duct and the peripheries ofthe operative rolls, a space within which the metal powder travels onthe surface of the lower roll from the feeding duct to the gap betweenthe operative rolls, this space being in communication with thereceiving duct, and the mill further comprising means for supplying aprotective gas to the receiving duct and the space enclosed by the coverand the feeding duct.

3. A rolling mill as claimed in claim 1, further comprising jacketsenclosing the operative rolls, but not enclosing the rollers that bearagainst the peripheries of the operative rolls, and burners for heatingthe rolls, located between the roll peripheries and the jackets.

References. Cited in the file of this patent UNITED STATES PATENTS1,380,632 Bowden June 7, 1921 1,556,658 Williams Oct. 13, 1925 1,667,884Cremer May 1, 1928 1,792,999 Messner Feb. 17, 1931 2,134,366 Hardy Oct.25, 1938 2,170,732 Sendzimir Aug. 22, 1939' 2,197,022 Petterson Apr. 16,1940 2,271,459 McConnell Jan. 27, 1942 2,287,663 Brassert June 23, 19422,341,732 Marvin Feb. 15, 1944 2,693,012 Harris et a1. Nov. 2, 19542,717,419 Dickey Sept. 13, 1955 2,771,637 Silvasy etal. Nov. 27, 1956

